1. Field of the Invention
The present invention relates to image-capturing apparatuses detachably mounted with lens apparatuses having mechanical shutters, lens apparatuses, image-capturing systems, methods for controlling image-capturing apparatuses, and methods for controlling lens apparatuses.
2. Description of the Related Art
Video cameras, especially those having interlaced imaging devices, such as CCD (Charge Coupled Device) sensors, are capable of shooting not only movies but also fine still images by employing mechanical shutters (see, for example, Japanese Patent Laid-Open No. 2004-724383 (paragraphs 0019 to 0020, FIG. 1) and Japanese Patent Laid-Open No. 2003-169248 (paragraphs 0021 to 0024, FIG. 1)).
In addition, lens apparatuses, which are detachably mounted on video camera systems (i.e., image-capturing apparatuses), having mechanical shutters have been suggested. Furthermore, a continuous shooting function has been introduced to such video cameras. With this feature, users can continuously shoot a plurality of still images by continuously pressing a still image recording switch disposed on such video cameras.
However, to perform a continuous shooting operation with a lens apparatus having a mechanical shutter and an image-capturing apparatus having a continuous shooting function, several conditions have to be met. First, the timing of an opening and closing operation of the mechanical shutter performed in the lens apparatus and that of a continuous shooting operation performed in the image-capturing apparatus have to be synchronized. And second, the opening and closing operation of the mechanical shutter and the continuous shooting operation in the image-capturing apparatus have to be repeated at the same speed.
More specifically, when the image-capturing apparatus has continuous shooting speed of 5 fps (frames per second), the lens apparatus has to perform the opening and closing operation of the mechanical shutter at a speed corresponding to 5 fps. However, synchronization of the timing of the continuous shooting operation and that of the opening and closing operation may be insufficient. Also, the maximum continuous shooting speed of a mechanical shutter varies among different lens apparatuses. For example, the lens apparatus may have a recommended value for the continuous shooting speed (i.e., maximum continuous shooting speed) of less than 5 fps. The recommended value is determined taking the durability of the mechanical shutter into account. In such a case, it is not preferable to perform the opening and closing operation of the mechanical shutter at a speed of 5 times per second or more, exceeding the recommended value, even if an instruction is given by the image-capturing apparatus.
Therefore, it would be desirable for an image-capturing apparatus to capture as many still images as possible in continuous shooting at a speed not exceeding the maximum continuous shooting speed of the mechanical shutter disposed in each lens apparatus.